Molecular sieves are a commercially important class of crystalline materials. They have distinct crystal structures with ordered pore structures which are demonstrated by distinct X-ray diffraction patterns. The crystal structure defines cavities and pores which are characteristic of the different species.
Molecular sieves identified by the International Zeolite Associate (IZA) as having the structure code CHA are known. For example, the molecular sieve known as SSZ-13 is a known crystalline CHA material. It is disclosed in U.S. Pat. No. 4,544,538, issued Oct. 1, 1985 to Zones, which is incorporated by reference herein in its entirety. In U.S. Pat. No. 4,544,538, the SSZ-13 molecular sieve is prepared in the presence of N,N,N-trimethyl-1-adamantammonium cation which serves as a structure directing agent (“SDA”), also known as on organic template. However, this SDA is costly, which makes the synthesis of SSZ-13 using this SDA costly. This cost can limit the usefulness of SSZ-13 in commercial processes. Thus, it would be desirable to find a way to synthesize SSZ-13 without having to use the costly N,N,N-trimethyl-1-adamantammonium cation SDA.
One way of reducing the amount of the N,N,N-trimethyl-1-adamantammonium cation SDA in the synthesis of SSZ-13 is disclosed in copending Provisional Application No. 60/826,882 filed Sep. 25, 2006 by Zones. There, the amount of N,N,N-trimethyl-1-adamantammonium cation SDA needed to synthesize SSZ-13 is reduced significantly by the addition to the SSZ-13 reaction mixture of benzyl trimethylammonium cation (e.g., benzyl trimethylammonium hydroxide). While this synthesis method can provide significant cost savings, it still requires the use of the costly N,N,N-trimethyl-1-adamantammonium cation SDA.
It has now been found that SSZ-13 can be prepared using benzyl trimethylammonium cation (“BzTMA cation”) in the absence: of a 1-adamantammonium cation, such as N,N,N trimethyl-1-adamantammonium cation.
U.S. Pat. No. 5,558,851, issued Sep. 24, 1996 to Miller, discloses a method for preparing a crystalline aluminosilicate zeolite from a reaction mixture containing only sufficient water so that the reaction mixture may be shaped if desired. In the method, the reaction mixture is heated at crystallization conditions and in the absence of an external liquid phase, so that excess liquid need not be removed from the crystallized material prior to drying the crystals. U.S. Pat. No. 5,558,851 is incorporated by reference herein in its entirety.